It is well known in the prior art for a host computer to assert control of a local microprocessor device for downloading of application program or configuration control data. Generally, if the local device has a keyboard or includes a program switch setting, either a specific program switch is set or a prearranged coincident press of plural keys during power up of the device is used to signal the local device to enter a host control mode. Thereafter the local device will accept control signals and data from a host computer via a communication channel connecting the two systems.
FIG. 1 illustrates a prior art system in which a host computer 5 is coupled via a data communication bus or channel 6 with a local device 8 which has a microprocessor board 8 (or microcontroller). In this case a set of switches 9 is provided and one of these switches would be devoted the host control mode and be set on to enter that mode. Then when the host control operation is completed, the switch would be returned to the off position to resume normal operation of the local device.
Some local devices such as the check reader 10 shown in FIG. 2 do not require switches or keyboards in their normal operation and including one of them for the sole purpose of achieving host control is an unattractive cost addition. If a switch were utilized in such a device for this purpose, it would usually be hidden under the case of the device to avoid inadvertant change of operation mode from normal operation to host control mode of operation. Thus, the case must be removed or a window in the case provided to gain access to the switch to change the mode.